1. Field of the Invention
The present invention relates to an image processing technique in an image capturing apparatus, an image processing apparatus or the like, and more particularly to a technique of correcting a chromatic aberration caused by an image capturing optical system on an image signal obtained by photoelectrically converting a light image entered via the image capturing optical system.
2. Description of the Background Art
In an image capturing apparatus such as a digital camera, a light image from the subject is led to an image capturing device such as a CCD via an image capturing optical system (taking lens).
In recent years, as reduction in the size of an image capturing device and increase in pixel resolution advance, aberration correction conditions requested for an image capturing optical system are becoming severer from the viewpoint of designing. In addition, miniaturization is demanded also for the image capturing optical system and designing of the optical system is becoming severer.
A particularly obtrusive aberration among the aberrations of the image capturing optical system is a magnification chromatic aberration (hereinafter, also simply referred to as chromatic aberration). Examples of known techniques of correcting a magnification chromatic aberration by image processing include a technique of correcting a magnification chromatic aberration by storing outputted image signals for each of color components of R (red), G (green) and B (blue) into a memory and moving and synthesizing the image signal on a pixel unit basis in accordance with the state of zooming and focusing of a taking lens (for example, Japanese Patent Application Laid-Open No. 5-3568 (1993) (hereinafter, referred to as Patent Literature 1)), and a technique of constructing an image capturing device by four CCDs and correcting a magnification chromatic aberration in accordance with the position of each CCD (for example, Japanese Patent Application Laid-Open No. 6-350904 (1994) (hereinafter, referred to as Patent Literature 2).
As disclosed in Japanese Patent Application Laid-Open No. 2002-209224 (hereinafter, referred to as Patent Literature 3), when a single-chip color image capturing device such as a CCD is used as an image capturing device, only a charge corresponding to one of primary color components of the three primary colors is accumulated in each pixel. Consequently, in order to obtain signals of color components of all of R, G and B with respect to each pixel, a color interpolating process (pixel interpolating process) has to be performed.
Even when one of the techniques of Patent Literatures 1 and 2 is used, the following problem occurs. Specifically, in any of the techniques of Patent Literatures 1 and 2, a chromatic aberration correcting process is performed after a color interpolating process. After a color interpolating process is performed on an image including a chromatic aberration, the chromatic aberration correcting process is performed. It is therefore difficult to make the chromatic aberration correction properly and sufficiently function. As a result, although the chromatic aberration correcting process is performed also in the conventional techniques, a problem such that a chromatic aberration is still conspicuous in a reproduced image occurs.
Conventionally, it is not considered to reduce a storage amount at the time of storing parameters and the like used at the time of correcting a chromatic aberration. When the pixel density of an image capturing device is conspicuously increasing as in recent years, the capacity necessary to store parameters and the like becomes enormous. It hinders reduction in the size of an apparatus and also causes a problem such as an increase in cost.